I did LHR-SIN-PER-SIN-LHR in May over a weekend - in Y - just to get my 4 QF sectors... out Friday PM arrive back Monday AM in time for work.
Wasn't able to get a legroom seat - and I have to say it was the most uncomfortable 48hrs I can remember.
I chose PER as cost-wise it was on-par with LHR-FRA-SIN-FRA-LHR or even MAN-LHR-PAR-LHR-MAN - but clearly yielded the most miles.
However, if I have to do it again (on account of missing the traditional annual pilgrimage, if someone doesn't shoot me) I will have to see past the miles and opt for one of the shorter routings.